Exeter Rocks is a famous place. A bay of the sea, almost a perfect semicircle, guarded by the reef: shelving white sands to span the few feet from the water to the under-cut turf: and then, almost at the mid point, a jutting-out shelf of rocks right into deep water--fathoms deep. And a narrow fissure in the rocks, leading the water into a small pool, or miniature lagoon, right inside their bastion. There it was, safe from sharks or drowning, that the Fernandez children meant to soak themselves all day, like turtles in a crawl. The water of the bay was as smooth and immovable as basalt, yet clear as the finest gin: albeit the swell muttered a mile away on the reef. The water within the pool itself could not reasonably be smoother. No sea-breeze thought of stirring. No bird trespassed on the inert air. For a while they had not energy to get into the water, but lay on their faces, looking down, down, down, at the sea-fans and sea-feathers, the scarlet-plumed barnacles and corals, the black and yellow schoolmistress-fish, the rainbow-fish--all that forest of ideal Christmas trees which is a tropical sea-bottom. Then they stood up, giddy and seeing black, and in a trice were floating suspended in water like drowned ones, only their noses above the surface, under the shadow of a rocky ledge. An hour or so after noon they clustered together, puffy from the warm water, in the insufficient shade of a Panama fern: ate such of the food they had brought as they had appetite for; and drank all the water, wishing for more. Then a very odd thing happened: for even as they sat there they heard the most peculiar sound: a strange, rushing sound that passed overhead like a gale of wind--but not a breath of breeze stirred, that was the odd thing: followed by a sharp hissing and hurtling, like a flight of rockets, or gigantic swans--very distant rocs, perhaps--on the wing. They all looked up: but there was nothing at all. The sky was empty and lucid. Long before they were back in the water again all was still. Except that after a while John noticed a sort of tapping, as if some one were gently knocking the outside of a bath you were in. But the bath they were in had no outside, it was solid world. It was funny. By sunset they were so weak from long immersion they could barely stand up, and as salted as bacon: but, with some common impulse, just before the sun went down they all left the rocks and went and stood by their clothes, where the ponies were tethered, under some palms. As he sank the sun grew even larger: and instead of red was now a sodden purple. Down he went, behind the western horn of the bay, which blackened till its water-line disappeared and substance and reflection seemed one sharp symmetrical pattern. Not a breath of breeze even yet ruffled the water: yet momentarily it trembled of its own accord, shattering the reflections: then was glassy again. On that the children held their breath, waiting for it to happen.